1. Field of the Invention
The present invention relates to an optical pickup actuator used for an optical recording and reproducing apparatus. More particularly, to a slim-type 3-axis driving optical pickup actuator using a fine pattern coil (FPC).
2. Description of the Related Art
A conventional optical pickup is used for an optical recording and reproducing apparatus and performs recording and/or reproduction of information in a non-contact manner with respect to an optical disk (i.e., an information storage medium). The optical pickup requires an optical pickup actuator capable of driving an objective lens in a track direction, a focus direction, and/or a tilt direction to form an optical spot at a correct position on the optical disk.
As high density optical disks become popular, the optical pickup and optical pickup actuator tend to be compact and light. In particular, for the optical pickup actuator to perform the recording/reproducing of information with respect to the high density optical disk, 3-axis driving, i.e. driving in the track direction, the focus direction, and the tilt direction, is necessary. Also, to make the optical pickup compact and light, the size of the optical pickup actuator needs to be small. Accordingly, an optical pickup actuator using a fine pattern coil capable of driving in three axes is needed.
FIGS. 1-3 illustrates a conventional optical pickup actuator using a fine pattern coil. As shown in FIG. 1, the conventional optical pickup actuator includes a base 1, a blade 5 supported by a suspension 3 and installed on the base 1 to be capable of moving, a magnetic circuit 10 dividedly installed on the blade 5 and the base 1, and a stopper 9 restricting a driving height during the driving of the blade 5.
An objective lens 7 is installed on the blade 5. As the blade 5 is driven by a driving force through the magnetic circuit 10, the objective lens 7 is driven in the track direction, the focus direction, and the tilt direction.
Thus, the magnetic circuit 10 includes a fine pattern coil 11 fixed to the blade 5, a pair of magnets 15 arranged to face each other with respect to the fine pattern coil 11 interposed therebetween, and a yoke 17 fixing the magnet 15 to the base 1 and forming a magnetic path. The magnets 15 are 2-pole magnetized permanent magnets. In FIGS. 1-3, the magnets 15 are illustrated as being surface polarized to the left and right.
The fine pattern coil 11 is divided into focus coils 12a and 12b and a track coil 13 according to the direction to drive the blade 5. The focus coil includes first and second focus coils 12a and 12b which are separated from a polarization line 15a of the magnet 15 that is polarized to the left and right. Thus, when current is applied, the focus coils 12a and 12b make the fine pattern coil 11 and the blade 5 driven in a Y-axis direction. To this end, the first and second focus coils 12a and 12b are arranged such that a part of the focus coils 12a and 12b parallel to the X-axis direction faces the magnet 15, and contribute to the driving in the focus direction. Thus, the other part (the lower portion in the drawing) of the focus coils 12a and 12b does not face the magnet 15 to prevent the offset of a driving force.
The track coil 13 is arranged in front of the polarization line 15a of the magnet 15 and drives the blade 5 in the X-axis direction when current is applied to the track coil 13. The track coil 13 is arranged such that a part of the track coil 13 parallel to a Y-axis direction faces the magnet 15, and contribute to the driving in the tracking direction.
In the conventional optical pickup actuator using a fine pattern coil configured as above, as shown in FIG. 3, when magnetic poles of the magnet 15 are arranged, an N pole and an S pole are respectively arranged in the left and right sides with respect to the polarization line 15a. When current is applied to the focus coils 12a and 12b in a direction indicated by arrows (→), the blade 5 is driven in a direction indicated by arrow (→).
In the above conventional optical pickup actuator, tilt driving is performed, not by including an additional tilt coil, but instead by using the first and second focus coils 12a and 12b. That is, input/output ports of current with respect to each of the first and second focus coils 12a and 12b are independently configured. Current of a different direction or intensity is applied to the input/output ports. Thus, the focus driving and tilt driving are performed using a difference in the driving forces.
Thus, since the conventional optical pickup actuator includes a structure to perform both focus driving and tilt driving using the first and second focus coils 12a and 12b, a drive circuit is complicated and a correction error may be generated when the driving to correct a focus error and the driving to correct a tilt error are simultaneously performed. Also, in the arrangement of the first and second focus coils 12a and 12b and the magnet 15, since only the upper portions of the first and second focus coils 12a and 12b are used, a magnetic force is weak.